Hello,

Was at track this past weekend and in between my run session I had the opportunity to get my car dyno'd again. The first time I dyno'd my car about 6 years ago I put down about 312rwhp/321tq. This time, I put down 320rwhp/332tq which is due to my electric cut out that I added and GM performance timing timing chain. The guy who dyno'd my car said that it was running kinda lean and that I should richin it up. Anyone have any thoughts on how much more power I could squeeze with the proper A/F ratio.

Here is my dyno sheet





Thanks,

 

Lean is power, and you're not lean up past 4500, even though the pic is small you look to be right at stoic so going any richer is just going to hurt power as long as you're not getting into detonation.

 

Ok good to hear, the tech was suggesting that I adjust my fuel pressure to enrich the ratio. He seemed to think that there was more power to be made. Even if I was to adjust the pressure, wouldnt the ecu change the injector duty cycle to meet optimal performance? I thought I read about this somewhere.

 

If you up the pressure, the long term fuel corrections will drop, pulling the extra fuel back out. But that's in closed loop, and you don't operate in closed loop at WOT. You go into power enrichment (PE) mode, and the PCM calculates a new target A/F ratio. Since your learned long term fuel corrections are (PROBABLY) going to be negative, subtracting fuel, the PCM will not use them in PE mode. So there is a good chance it will richen it up.

But.... that's not the way to do it - sort of hit or miss. If your engine is running on the lean side in closed loop, requiring positive long term fuel corrections to bring it back to stoichiometric, even with higher fuel pressure, the long terms may be positive, and now the PCM will use those long terms in PE mode - no increased richness.

Have a tuner adjust the tables that the PCM uses to calculate the target A/F ratio in PE mode.

But as noted above, there is no indication, given the limitations of the small size of the chart we are looking at, to indicate it needs to run richer. The reason they put the dashed line at 13:1 is to indicate where its most likely to make the best power/torque.

 

Thanks for the explanation on this. At this point I think I leave it as is until I start messing with the heads. Then It will make sense to spend the $$$ to get it tuned on the dyno. Overall, I'm happy to see that the engine is outputing more power that before. Not sure if the GM roller chain was the cause or if it was the electric cut out.

Best,

 

you gained it in the cutout most likely... a timing chain doesnt gain anything except maybe a tad bit less rolling resistance in the chain? but id think that wouldnt really be worth anything